Core for pressure-sensitive adhesive tape



Jan. 23, 1968 P. N. GUSTAFSON 5 CORE FOR PRESSURE-SENSITIVE ADHESIVETAPE Original Filed March 26, 1962 INVENTOR. B404 MGUJTAFJU/Y BY W KMfirm/ma United States Patent Ofitice 3,364,955 Patented Jan. 23, 168

3,364,955 CORE FOR PRESSURE-SENSITIVE ADHESIVE TAPE Paul N. Gustafson,St. Paul, Minn., assignor to Minnesota Mining and Manufacturing Company,St. Paul, Minn., a corporation of Delaware Original application Mar. 26,1962, Ser. No. 182,240, new Patent No. 3,204,763, dated Sept. 7, 1965.Divided and this application Feb. 24, 1965, Ser. No. 448,223

2 Claims. (Cl. 138-144) ABSTRACT OF THE DISCLOSURE A composite core for-a convolutely wound roll of sheet material, such as pressure-sensitiveadhesive tape, is made up of concentric annuli. When the sheet materialis Withdrawn from the roll and the inner annulus is held in fixedposition, the outer annulus rotates upon the inner. The core may be madeby slicing a composite tube formed from a plurality of spirally woundplies in which the interface between two plies is free of adhesive. Aply radially inward from the interface may be wound to leave a gapbetween adjacent edges, facilitating separation of annuli, if desired.

This application is a division of 'copending application Ser. No.182,240, now US. Patent 3,204,763.

Cores for pressure-sensitive adhesive tape are usually made from bulkyinexpensive materials which provide a desired degree of stiffness atminimum cost. A typical manufacturing procedure involves forming 'a tubeby spirally or helically winding seven or more plies of chipboard, jutepaper, or the like, on a cylindrical mandrel to a thickness of perhaps,4 an inexpensive adhesive, such as precooked dextrine dissolved inwater, being used to bond the plies together. The tube is then slit, orsliced, at right angles to its axis to form tape cores of the desiredwidth, the inner edges of the core being raised and roughened to someextent by the slitting operation. A common inner core diameter forindustrial tape is three inches.

In many industrial operations the uses of a roll of pressure-sensitiveadhesive tape holds the core in one 'hand, atfixes one end of the tapeto a surface to be masked or taped and then pulls vigorously on the rollof tape to quickly withdraw a suitable length thereof. In thisoperation, the tape core slides on the users hand, and the rough innersurface and somewhat abrasive edges tend to burn or scratch the skinwith which they come in contact. This source of irritation is a limitingfactor governing the speed with which some taping operations are per--formed. Attempts have been made to minimize the problem of friction andabrasion of the users hand by developing small dispensers which fitinside the tape core and provide a bearing surface against which thecore rotates. Such dispensers have not been widely used, however,because of their cost, particularly since many of them are likely to belost or broken in use. In addition, most such dispensers can be usedwith only one width of tape.

I have now devised an inexpensive but highly convenient tape core whichcan be held in the hand of the user, the rapid withdrawing of tapecausing no injury to the users hand. My novel tape cores are simple andeasy to fabricate, providing an inexpensive and highly efiectivesolution to a problem of long standing.

In accordance with my invention I form a composite annular tape corefrom two rotatably slidably contacting concentric annular membersinstead of the single annulus customarily employed. By this simple butunobvious means I provide a tape core which the user can hold, his

fingers contacting the inner annulus and holding it in fixed positionwhile the outer annulus revolves as tape is withdrawn. If desired, aroll of tape wound on such a core may be mounted on a dispenser and usedin the same manner as tape wound on a conventional core, thus providingan unusual degree of versatility.

My invention will be better understood upon reference to theaccompanying drawings, in which:

FIGURE 1 is a side view of one embodiment of my novel tape core, showinga roll of normally tacky and pressure-sensitive adhesive tape woundthereon;

FIGURE 2 is a view in perspective of "a preferred embodiment of myinvention, with certain portions being shown partially cut away forgreater clarity; and

FIGURE 3 is a view in perspective of a tube, in process of manufacture,from which the core shown in FIG- URE 2 can be sliced.

With reference to FIGURE 1, inner annulus 11 is snugly positioned insideouter annulus 12, contacting it along interface 13. An elongate strip ofnormally tacky pressure-sensitive adhesive tape 14 is convolutely woundupon itself on the outer circumference of annulus 12. A tape core ofthis type may be formed by only slightly modifying the conventionalmanufacturing process described in the second paragraph of thisdisclosure to provide two concentric annuli instead of the conventionalone. This result may be accomplished by either omitting the adhesivebetween two radially adjacent plies or replacing the adhesive with anoil or other material repellent to the water-based core adhesive used tounite the other plies, e.g., silicone resin, a Werner-type chromiumcomplex, or the like. As a further aid to insure the free rotation ofannulus 12 about annulus 11, it may be desirable to form one of the twoplies which contact to form interface 13 from a sheet material having acomparatively smooth surface, e.g., calendered parchment, plastic coatedpaper, or the like.

Free rotation of the outer annulus about the inner may also be aided byincreasing the degree of clearance be tween the two in various ways. Forexample, the inner annulus may be made of a shrinkable material, e.g., awet bulky ply which will contract to a greater degree upon drying thanwill the outer plies. The inner annulus may also be formed from anelastic material which is stretched slightly when it is wound about theforming mandrel, the relaxation which occurs when the tube is removedfrom the mandrel providing circumferential shrinkage of the innerannulus. It might be supposed that such an increase in the space betweenthe two annuli would cause the ultimately formed composite cores to fallapart by axial separation, either before or during use. As a matter ofpractice, however, such is not the case; the operation which slits thetubes into composite cores made according to my invention serves toproduce an edge on the outer annulus which is turned radially inwardenough to hold the inner annulus in position.

The embodiment of my invention shown in FIGURE 2 illustrates a tape corewhich is especially well suited for use either in conventionaldispensers or in hand operations of the type previously described. Splitring annulus 21 is snugly positioned inside outer annulus 22, theradially outer surface of the former and the radially inner surface ofthe latter contacting at interface 23. If desired, a strip of sheetmaterial 24, which may bear identifying indicia for tape wound on thecore, is firmly adhered to the radially inner surface of split ringannulus 21 so as to span gap 25, areas 24a and 24b indicating theportions of strip 24 located immediately adajcent to and on oppositesides of gap 25. structurally, strip 24 need be only wide enough toslightly more than span gap 25 and may be adhered to either the radiallyinner or radially outer surface of split ring annulus 21; in fact,

strip 24 may be wound to adhere to the radially inner part of one end ofsplit ring annulus 21 and to the radially outer surface of the otherend. Adhesion of strip 24 to annulus 21 may be low enough to permit itsremoval if desired. Any of the various means described in connectionwith FIGURE 1 may be employed to minimize friction at interface 23.

A roll of tape in which an elongate strip of normally tacky andpressure-sensitive adhesive tape is wound on the core shown in FIGURE 2may, if desired, be used in the same manner as a conventional roll oftape. Thus it may be firmly mounted on the expandable mandrel of aslitter or on a dispenser drum, the expanding action provided by themandrel or drum serving to force split ring annulus 21 into such firmcontact with outer annulus 22 that no slipping occurs at interface 23,rotation instead occurring about the axis of the mandrel or drum. If itis desired, however, to use the roll of tape for a hand operation, thecore may be readily and simply converted to adapt it for such use. Theoperator wishing to so employ the tape performs the following steps: (1)with his fingernail or the back of a knife blade he depresses paper ply24 into gap 25, and (2) gripping the roll of tape in both hands whileplacing one thumb at area 24a and the other at area 24b, he forces histhumbs toward each other at right angles to gap 25. This simple andquickly performed operation decreases the circumference of annulus 21 topermit ready rotation of outer annulus 22 about inner annulus 21. Tomake the two annuli freely rotatable as just indicated, gap 25 may be onthe order of /s" in width.

The core of FIGURE 2 is conveniently slit from a tube formed by theprocess indicated in FIGURE 3, in which strip 31, ply 33, and ply 35 aresuccessively wound about a cylindrical forming mandrel (not shown).Strip 31 may be wound so that its lateral edges contact smoothly at lineof abutment 32, but ply 33 is wound so that a gap 34 is deliberatelyleft between adjacent lateral edges, this gap occurring over strip 31.Strip 31 and ply 33 are adhesively secured together; adhesive is omittedbetween ply 35 and ply 33 to decrease frictional engagement, thewinding, however, being snug enough to prevent premature slipping. Ply35 is preferably wound in such a manner that its lateral edges abutsnugly along line 36. Succeeding plies are wounded over each other inthe same manner as ply 35 and adhesively secured to the underlyingplies.

The total number of plies employed is dependent upon the dimensions,stiffness, and strength of the individual plies, as well as upon theoverall dimensions and ,ultimate use of the core. I have found thatwhere my composite core is formed from seven plies of approximatelyequal thickness, the interface between the inner and outer annuli shouldgenerally occur between either the second and third or the third andfourth plies from the center of the core, counting any substantiallycontiguous innermost indicia-bearing strip as the first ply. In order toassure free rotation of the outer annulus about the inner, the outerannulus should be sufiiciently thick to keep it from collapsing duringthe operation in which adhesive tape is wound thereon. The inner annulusmust only be thick and strong enough not to collapse, tear, or abradeaway'from the pressures exerted by an operator in normal use. Althoughadditional thickness does not appear to be especially harmful, it tendsto detract from the economy of the core construction.

Many modifications and adaptations of my invention will be apparent tothose skilled in the art. For example, sheet material other thanpressure-sensitive adhesive tape, such as paper toweling, ribbon, tissuepaper, and similar sheet material either sold in roll form for manualhandling or mounted ona dispenser having a fixed core holder, mayadvantageously be wound on the novel core of this invention.Accordingly, patent protection is limited only by the scope of theappended claims.

What I claim is: I

1. A composite tube formed from a plurality of successively snuglyspirally wound adhesively united individual plies, the interface betweentwo of said plies being free from adhesive so as to provide an outer andan inner annulus, and a ply lying radially inward from said interfacebeing wound so as to leave a substantial gap between adjacent lateraledges, whereby cores for sheet material such as pressure-sensitiveadhesive tape may be formed by cutting said tube to appropriate lengths,the annuli of such cores being capable, when a roll of sheet materialwound thereon is unwound, of either rotating as a unit or, when thelateral edges of the radially inward ply are forced together to increasethe separation between annuli, rotating separately.

2. The tube of claim 1 in which, radially inwardly adjacent to said plyhaving a gap between adjacent lateral edges, is adhered a ply whichcovers said gap.

References Cited UNITED STATES PATENTS 2,350,369 6/1944 Sampair 206-592,659,543 11/1953 Guyer 242-68.5 2,888,043 5/1959 Reid 138-144 LAVERNED. GEIGER, Primary Examiner.

T. MOORHEAD, BRADFORD KILE,

Assistant Examiners.

